In a crockpot I suppose the rump (also known as a fresh ham) will be OK. Having made my pulled pork for about 40 years and tried fresh ham, I prefer the butt/shoulder/picnic cut of the pig.
And yes, we have whole hog BBQs (the noun--not the grill) where the whole pig is cooked overnight at a low temp--ribs, shoulder, hams, etc. It is delicious as well.

This is a definition of the rear leg. The front leg=shoulder/butt

pork leg = ham The meat from this part of the pig is usually made into hams, but fresh leg meat is lean and makes a terrific roast. Cuts:fresh pork leg = fresh ham = fresh leg of pork Notes: This makes a great roast for a large crowd. It's usually cured as ham, so you might have to special-order it to get it fresh. It's sold either boneless or bone-in, and either whole or halved. The bottom half is called the shank portion = shank roast = leg roast, while the upper is called a top leg roast = inside roast = butt portion = pork leg butt = fresh ham butt = pork leg roast sirloin portion. A steak cut from the leg is called a fresh pork leg steak. Substitutes: pork center loin roast OR pork sirloin roast OR Boston butt

Several people have PMed me asking questions about how to do my pulled pork. I am glad to reply but I wonder why they don't post on here so everyone can have the same answers if they had the same questions. Just a thought.

Several people have PMed me asking questions about how to do my pulled pork. I am glad to reply but I wonder why they don't post on here so everyone can have the same answers if they had the same questions. Just a thought.

Carolina Pulled porkI posted it a long time ago. It is truly easy and delicious.
1 pork shoulder or butt, bone in or out--any size--the cooking time is the same for a 3#or 8# piece. BBQ rub of your choice or just rub the meat with a mixture of coarse ground black pepper and brown sugar. Let marinate 8 hours or overnight.
Method 1--IF you have a smoker that can control the temp (I have a sidebox smoker and can keep the temp at 200*-250*) smoke the meat for 4 hours, keeping the temp low. Then place the meat in a 250* oven for 4 hours to finish. It will be meltingly tender and have a wonderful smoky flavor. Method 2 (and this is the one I have really used for 30 years). Place the meat in a 250* oven for 8 hours uncovered . I have often done them overnight. It will still have the melting tenderness. You will have to slap your hands to have any left over as you take it out of the oven.
When ready to serve pull chunks of meat off and then "pull" the meat into shreds by pulling between 2 forks. Do not discard the fat--mix it in. This is not a low fat dish and to really enjoy, use it!!!
For a traditional Carolina serving method very lightly moisten the meat with sweetened vinegar (1 qt. vinegar + 1/4C sugar and 2TBS coarse black pepper). To warm before serving put the vinegared meat in a pan (black iron frying pan is good) and cover tightly. Heat at 250* until heated.
To serve, offer bbq sauces, cole slaw (in the Carolinas, it goes ON the sandwich), baked beans, rolls, and banana pudding. For fall bbq's Brunswick Stew is also offered.
For BBQ sauce here is my tomato based:
1 bottle ketchup (28 or 32 oz.) 1 ketchup bottle of cider vinegar 6 oz. yellow mustard 6 oz. worcestershire sauce 1/2C brown sugar 3 oz. liquid smoke 2-3 TBS coarse black pepper Tabasco to your taste Simmer for 45 minutes.
If you use commercial bbq sauce I suggest diluting them 1/2 with vinegar for this use.
Eastern NC uses vinegar sauces--sweetened vinegar with 1/4C (at least!!) cayenne pepper OR black pepper. It is too hot for me! South Carolina uses a mustard based sauce but don't know the recipe.